Method of manufacture of bicarbonate of soda.



R. 'H. F. PINLAY. METHOD OF MANUFAGTURE OF BIOARBONATE OF SODA. APPLICATION FILED JULY 17. 1908.

Patented June 21, 1910.

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ROBERT HUG-H FORSYTHE FINLAY, 0F IBELFAST, IRELAND.

METHOD OF MANUFACTURE OF BICARBONATE OF SODA.

To all whom it may concern:

Be it known that 1, ROBERT HUGH Fon- SY'lI-IE FINLAY, a subject of the King of Great Britain, residing in Belfast, Ireland, have invented certain new and useful Improvements in the Method of Manufacture of Bicarbonate of Soda, of which the following is a specification.

This invention relates to improvements in 1 hydrogen formed at the same time as the the method of manufacture of bicarbonate of soda and it has for its object certain improvements in the ordinary or so-called Solvay ammonia-soda process, whereby I am enabled to dispense with the necessity for distilling the liquid from which the bicarbonate of soda has been precipitated (hereinafter called the mother liquor), avoid the use of lime, and the loss of ammonia and undecomposed salt contained in the discharge from the stills after distillation-.the disposal of which discharge constitutes rather a troublesome feature of the ammonia-soda process as now carried out.

The present invention moreover presents the important advantage that I am enabled to recover thechlorin of the salt acted upon, in the valuable form of chlorin gas, instead of as heretofore permitting it to pass away with the discharge abovc mentioned in the comparatively worthless form of calcium chlorid.

In carrying the invention into effect I follow the earlier steps of the well known ama after treatment with carbonic anhydrid, into the cathode chamber of an electrolytic cell,

" or battery of cells, constructed preferably after the manner set forth in thelilnited States Patent No. 850,867, brine being supplied at the same time into the other chamber or chambers. The ammonium. chlorid Specification of Letters Patent. Patented June 21', 1910,

Application filed July 17, 1908.

Serial No. 444,005.

in the mother liquor is here electrolyzed, and ammonia is set free at the cathode and combines with carbonic anhydrid, if present, chlorin being also set free at the anode. In some cases I adoptthe well known expedient. of introducing carbonic acid to the cathode chambers by a pipe.

After electrolysis I remoive the liquids and gases from. the cathode chambers. The

ammonia is readily eliminated, being insoluble. Water also may be eliminated from the liquid by evaporation at this stage. The liquid which now contains some common salt and the ammonium chlorid which has not been decomposed by electrolysis may be used instead of brine in the first reaction of the process in which meeting with the ammonia liberated by electrolysis and carbonic anhydrid, bicarbonate of soda is again precipitated and the mother liquor again treated as described. V

If salt be added to the mother liquor before, and carbonicanhydrid be injected during electrolysis, bicarbonate of soda may be formed in the cathode chamber of the cell. In this case the chamber should be made larger than would otherwise be necessary and be furnished with suitable means for removing the precipitate.

In order that the invention may be the better understood reference is made to the accompanying drawings showing a digrammatic representation of one element consisting of one anode, one cathode, one anode chamber, one cathode chamber, and one electrolyte chamber together with the necessary pipes and fittings used in connection with the preferred arrangement ofelect-rolytic cell 1 adopt.

In the accompany drawings A indicates the anode, and B indicates the cathode.

U and D are diaphragms and E is the electrolyte chamber.

F is the anode chamber and G the cathode chamber, and H and K indicate vessels for separating the liquids and gases which come from the anode and cathode chambers.

I is a vent to take away overflow from anode chamber and L is a vent for the cathode chamber. M indicates the brine cistern supplying electrolyte chamber and N a column liquid at the same level as in M producing pressure on electrolyte chamber.

0 represents means for supplying the liquid containing ammonium chlorid to the cathode chamber and P is a pipe for supplying carbonic anhydrid to said cathode chamber. I

Q represents means for removing the b1- carbonate of soda precipitated in cathode chamber.

' In operation F and E are filled with brine, G is filled with liquor containing ammonium chlorid. The head on E causes brine to ass through diaphragm G to F likewise to G, all the. time the apparatus is in use, I and L being always open to prevent the pressure in F and G rising, and to allow the liquids entering F and G to pass out again.

\Vhen the electric current is on, chlorin is evolved at A in small bubbles which pass over into H carrying with them a quantity of the liquid in F; Here (in H), the separation of the gas and the liquid takes placethe chlorin passing out at the top and the liquid at the bottom of the separator H. This liquid returning immediatel to F causes a vigorous circulation in The liquid passing away at I is the brine which passes through C (from E to ,F- as explained) deprived of a portion of itssalt-bythe electrolysis. In like manner hydrogen and ammonia are evolved on B, the hydrogen passes into K and escapes at its upper end, the liquor it carries with itpasses opt.

at its lower end, and back to G aga n causing avigorous circulation. The ammonia is found dissolved in the liquid which comes away at L and partly in the gas coming away at the top of K from which gas it'is recovered by well known means. The common salt is dissolved in the liquid from L, and carbonic acid is added to produce a precipitate of bicarbonate of soda. The ammonium chlorid liquor is fed at 0 all the time the electric current is on and the quantity supplied at O is proportioned to the current employed.

Another method is to 'pass carbonic anhydrid into G through P otherwise the 'process is similar. This combines with the ammonia formed on Band reduces the elec} tromotive force required for the cell. If the ammonium chlorid liquor in this case is saturated with common salt before entering bicarbonate of soda is precipitated in (lr and ma be removed at Q. Some may pass out at with the other compounds formed in G all of which are recovered and utilized.

by well-known means.

It will be seen that in my improved am monia-soda process I decompose the ammonium chlorid in the mother liquor in a suitable electrolytic cell or battery of cells so as to recover the ammonia therefrom and renmother liquor to electrolysis in the cathode chamber of a cell separated by one or more diaphragms from the anode chamber which is filled with sodium chlorid solution for the purpose of recovering the ammonia and obtaining hydrogen and chlorin; I

2. In the manufacture of bicarbonate of soda by the Solvay process, subjecting the mother liquor, after the addition of sodium chlorid, to electrolysis in the cathode chamber of a cell, separated by one or more diaphragms from the anode chamber which is filled with sodium chlorid solution for the purpose of recovering the ammonia and obtaining hydrogen and chlorin.

3. In the manufacture of bicarlfonate of soda by the Solvay process, subjecting the mother liquor to electrolysis in the cathode chamber of a cell which is supplied with carbonic anhydrid and which is separated by one or more diaphra ms from the anode chamber which is fille with sodium chlorid solution for the purpose of recovering the ammonia and obtaining hydrogen and chlorin.

4. In the manufacture of bicarbonate of soda by the Solvay process, subjecting the mother liquor after the addition of sodium chlorid, to electrolysis in the cathode chamber of a cell, which is supplied with carbonic anhydrid and which is separated by one or more diaphragms from the anode chamber which is filled with sodium chlorid'solution for the purpose of recovering the ammonia and obtaining hydrogen andchlorin.

5. In the manufacture of bicarbonate of soda by the Solvay process, subjecting the mother liquor to electrolysis in the cathode chamber of a cell separated by one or more diaphragms from the anode chamber which filled with a sodium salt solution for the purpose of recovering the ammonia and obtaining hydrogen and chlorin.

(5; In themanufacture of bicarbonate of soda by the Solvay proeess, subjecting the 'taining hydrogen and chlorin.

7. In t e manufacture of bicarbonate (if soda by the Solva process, subjecting the mother liquor to e eetrolysis in the cathode chamber of a cell which is supplied with carbonic anhydrid and Which is separated by one or more diaphragnis from the anode.

chamber which is filled with a sodium salt solution for the purpose of recovering the Signed at Belfast this first day of July 1908, in the presence of the two undermentioned Witnesses.

ROBERT HUGH FORSYTHE FINLAY Witnesses WILLIAM JAMES GRAHAM, HENRY STURGEON. 

